# Directory github.com/ooni/probe-cli/internal/engine/experiment This directory contains the implementation of all the supported experiments, one for each directory. The [OONI spec repository contains a description of all the specified experiments]( https://github.com/ooni/spec/tree/master/nettests). Note that in the OONI spec repository experiments are called nettests. Originally, they were also called nettests here but that created confusion with nettests in [ooni/probe-cli]( https://github.com/ooni/probe-cli). Therefore, we now use the term experiment to indicate the implementation and the term nettest to indicate the user facing view of such implementation. Note that some experiments implemented here are not part of the OONI specification. For example, the [urlgetter](urlgetter) experiment is not in the OONI spec repository. The reason why this happens is that `urlgetter` is an experiment "library" that other experiments use to implement their functionality. Likewise, the [example](example) experiment is a minimal experiment that does nothing and you could use to bootstrap the implementation of a new experiment. Of course, this experiment is not part of the OONI specification.